The miniaturization of semiconductor devices and the like is advantageous in bringing about an improvement in performance and function (higher-speed operation, lower power consumption, etc.) and a reduction in cost and thus has been accelerated more and more. The lithography technique has been supporting this miniaturization and transfer masks are a key technique along with exposure apparatuses and resist materials.
In recent years, the development of the half-pitch (hp) 32 nm generation according to the semiconductor device design rule has been progressing. This corresponds to ⅙ of a wavelength 193 nm of ArF excimer laser exposure light. In the hp32 nm and subsequent generations, only the application of the resolution enhancement technology (RET) such as the conventional phase shift method, oblique illumination method, and pupil filter method and the optical proximity correction (OPC) technique is becoming insufficient, and the hyper-NA technique (immersion lithography) and the double exposure (double patterning) technique are becoming necessary.
In the case of manufacturing a photomask having a mask pattern of a light-shielding film on a transparent substrate, when the light-shielding film (e.g. a Cr-based single-layer film or a laminated film of a plurality of Cr-based layers) is dry-etched using a resist film formed with the mask pattern as a mask, the resist film is also etched to be consumed. Therefore, the resolution when the mask pattern is transferred to the light-shielding film is lowered.
As a measure for this, it is effective to reduce the thickness of the light-shielding film. However, if the thickness of the light-shielding film is reduced, the OD value (optical density) decreases.
As a measure for the above, a method of Patent Document 1 has been proposed. This method uses, for example, a blank in which a MoSi-based light-shielding film and a Cr-based etching mask film (also serving as an antireflection film) are formed on a substrate (see the same document, paragraph [0174] etc.). Using the Cr-based etching mask film with a small thickness, the load to a resist is reduced so that a reduction in resolution when a mask pattern is transferred to the Cr-based etching mask film with the small thickness is improved. Along with this, using as an etching mask for the light-shielding film the etching mask film having higher etching selectivity than the resist with respect to the light-shielding film and having the thickness much smaller than that of the resist, an improvement in CD of a light-shielding film pattern is intended to be achieved. In this event, OD=3 of the light-shielding film is also ensured. However, it is not intended to reduce the thickness of the MoSi-based light-shielding film itself.
On the other hand, Patent Document 2 describes, as a light-shielding film having a laminated structure of MoSi-based materials, a light-shielding film having a laminated structure of a MoSiN main light-shielding layer and a MoSiON antireflection layer from the substrate side, or the like, for example.    Patent Document 1: JP-A-2007-241065    Patent Document 2: JP-A-2006-78807